Thermogravimetric Apparatus Research Articles

Comparison Study of Oxidation Behavior of Copper at Elevated Temperatures

The oxidation rate of pure copper was measured for 48 hours over the temperature range of 500°C to 700°C using thermogravimetric apparatus by means of continuous and discontinuous oxidation methods. It was found that weigh-gained of both samples was found to be increased with increasing temperature and rate laws were determined to be parabolic and linear rate law each other. The comparison of oxidation rate of copper was shown to be higher in discontinuous that in continuous process due to direct oxidation through the oxide scale and copper substrate.

Pyrolysis behavior of biomass with different Ca-based additives

CaO is an important catalyst in biomass gasification and pyrolysis. However, CaO can stem from many precursors. And, the effect between different precursors has still not been studied. Calcined natural limestone, natural dolomite, calcium oxide, calcium carbonate, calcium acetate, and calcium propionate were used to investigate their pyrolysis reactivity of biomass (peanut shells and pine sawdust) at high temperature (>800 °C). Experiments were conducted using a thermogravimetric apparatus and a fixed-bed pyrolysis system. Pine sawdust displayed higher pyrolysis reactivity than peanut shells. During pyrolysis, Ca-based additives fixed carbon dioxide mainly in the temperature range of 300–700 °C. By addition of Ca-based additives, the concentrations of hydrogen and carbon monoxide were increased and the concentrations of methane and carbon dioxide (over 18 vol%) were decreased. De-carbonation started around 700 °C. The emission of CO2 by de-carbonation promoted the reduction of char by the Boudouard reaction and methane by the dry reforming reaction. The total pyrolysis conversion decreased as PI-Dol > PI-CaA > PI-Lime > PI-Ca > PI-CaP > PI Raw > PI-CaC. The excellent pyrolysis reactivity of biomass in the presence of calcined calcium acetate can be ascribed to its preeminent physical structure. Addition of Ca-based additives increased the activation energy of the main devolatilization region. The activation energy of biomass with calcined natural dolomite, about 110 kJ mol−1, was much lower than that of other Ca-based additives studied at high temperatures. Pyrolysis of the pure biomass sample can be simply hypothesized as a first order reaction, but it varied significantly with the addition of additives.

Feather Keratin Deposits as Biosorbent for the Removal of Methylene Blue from Aqueous Solution: Equilibrium, Kinetics, and Thermodynamics Studies

Development and utilization of low-cost and effective adsorbents for the adsorption processes is a research focus in recent years. In this work, the porous and flexible film was prepared without any pretreatment from the feather keratin deposits produced during the extraction of soluble keratin from chicken feathers. Characteristics of the prepared biosorbent were investigated using thermogravimetric apparatus, X-ray diffraction, Fourier transform infrared, and scanning electron microscopy. Batch adsorption assays were carried out to remove methylene blue (MB) from aqueous solution. The results showed that the extent of MB adsorption on the biosorbent increased with an increase in initial dye concentration, contact time, solution pH, and biosorbent dosage. The equilibrium data were best described by Langmuir isotherm than other isotherm models. The maximum monolayer adsorption uptake was 156.5 mg/g at pH 7 for an initial dye concentration of 200 mg/l. Kinetic studies indicated that the adsorption process of MB followed pseudo-second-order kinetics. Nevertheless, the intra-particle diffusion model confirmed that the adsorption of MB was a two-step process: a rapid surface adsorption followed by intra-particle diffusion. Thermodynamic parameters such as ΔG°, ΔH°, and ΔS° were calculated, indicating that the adsorption process was spontaneous and endothermic.

Human collagen-based multilayer scaffolds for tendon-to-bone interface tissue engineering

The natural tendon-to-bone region has a gradient in structure and composition, which is translated into a spatial variation of chemical, physical, and biological properties. This unique transitional tissue between bone and tendon is not normally recreated during natural bone-to-tendon healing. In this study, we have developed a human collagen-based multilayer scaffold mimicking the tendon-to-bone region. The scaffold consists of four different layers with the following composition gradient: (a) a tendon layer composed of collagen; (b) an uncalcified fibrocartilage layer composed of collagen and chondroitin sulfate; (c) a calcified fibrocartilage layer composed of collagen and less apatite; (d) a bone layer composed of collagen and apatite. The chemical, physical, and mechanical properties of the scaffold were characterized by a scanning electron microscope, porosimeter, universal tensile machine, Fourier transform infrared spectrometer, energy dispersive X-ray analysis apparatus, and thermogravimetric analysis apparatus. The multilayer scaffold provided a gradual transition of the physical, chemical, and mechanical environment and supported the adhesion and proliferation of human fibroblasts, chondrocytes, and osteoblasts toward each corresponding matrix. Overall, our results suggest the feasibility of a human collagen-based multilayer scaffold for regeneration of hard-to-soft interface tissues.

Reduction and Oxidation Kinetics of a CaMn0.9Mg0.1O3−δOxygen Carrier for Chemical-Looping Combustion

The objective of this study was to establish the reaction kinetics involved in redox cycles of the CaMn0.9Mg0.1O3−δ material to be used as an oxygen carrier in the chemical-looping-combustion process. The oxygen-transport capacity and reactivity of this material during consecutive reduction and oxidation steps with gaseous compounds (CH4, H2, CO, and O2) were studied in a thermogravimetric analysis apparatus. The oxygen uncoupling properties of this material were also analyzed. It was found that material reactivity increased with the number of redox cycles, whereas the oxygen-transport capacity decreased with the cycle number until it was stabilized or “activated”. Conversion versus time curves at different temperatures (973–1273 K) and reacting gas concentrations (5–60 vol %) were used for kinetic determination. The grain model with control by chemical reaction and diffusion through the product layer was used to obtain the kinetic parameters for fresh and “activated” particles.

Performance of Natural Sorbents during Calcium Looping Cycles: A Comparison between Fluidized Bed and Thermo-Gravimetric Tests

Six European limestones and one European dolomite were tested for CO2 capture by simulating calcium looping cycles both in a lab-scale fluidized bed (FB) and in a thermo-gravimetric (TG) apparatus. The FB tests were carried out under severe conditions representative of a process with calcination in an oxy-firing environment (T = 940 °C, 70% CO2). The TG tests were performed with a somewhat milder calcination environment (T = 900 °C, 15% CO2). Carbonation conditions were the same for the two types of experiments (T = 650 °C, 15% CO2). The effect of the presence of SO2 (during both calcination and carbonation) at two different concentration levels was also studied in both devices. The aim of these experiments was to select the best sorbents for further larger scale testing and to establish if TG testing is representative of results obtained under more realistic FB conditions, with regards to CO2 capture capacity and overall ranking of the sorbents. Results showed that the CO2 capture capacity of the sorbent...

Facile synthesis and performances of PEG/SiO2 composite form-stable phase change materials

A facile route based on ultrasound-assisted sol–gel method has been developed and applied to rapid synthesis of polyethylene glycol (PEG)/silicon dioxide (SiO2) composite form-stable phase change materials (PCMs) without co-solvent and surfactant. This method was carried out under ultrasonic power of 300W using HCl and Na2CO3 as the acidic and alkaline catalyst, respectively. The temperature is below 50°C. The PCMs were characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), Differential Scanning Calorimetry (DSC) and thermogravimetric analysis apparatus (TGA) measurements. The PCMs display low density, high volume energy density, excellent form-stable effect, good phase-change and temperature control performance, which are very important for the actual application of PCMs in energy-saving construction materials.

Oxidation Study on the Fabrication of Fe-36Ni Oxide Powder from Its Scrap

A study of oxidation kinetic of Fe-36Ni alloy has been investigated using thermogravimetric apparatus (TGA) in an attempt to define the basic mechanism over a range of temperature of 400 to and finally to fabricate its powder. The oxidation rate was increased with increasing temperature and oxidation behavior of the alloy followed a parabolic rate law at elevated temperature. Temperature dependence of the reaction rate was determined with Arrhenius-type equation and activation energy was calculated to be 106.49 kJ/mol. Based on the kinetic data and micro-structure examination, oxidation mechanism was revealed that iron ions and electrons might migrate outward along grain boundaries and oxygen anion diffused inward through a spinel structure, .

Modulation of the acidity of niobic acid by ion-doping: Effects of nature and amount of the dopant ions

The acidity of niobic acid (NBO) has been successfully mitigated and tuned by addition of K+, Ba2+ and Nd3+ dopant species in amounts from 1 to 15atomnm−2. The characterization of the intrinsic acid properties of the samples was performed by adsorption of NH3 in a volumetric–microcalorimetric coupled line and by temperature programmed desorption (TPD) of 2-phenylethylamine in a thermogravimetric apparatus. The K-dopant was more effective in decreasing the acidity of niobic acid than the Ba- and Nd-dopants. Complementary measurements of the effective acidity of the samples in water by base titrations with 2-phenylethylamine completed the study and revealed a different picture of the effect of the three dopants on the NBO acidity in water.All the results indicated that the K-dopant targeted more selectively the Brønsted acid sites, acting as an ion-exchanger, while Ba- and Nd-species predominantly acted on the Lewis acid sites of the NBO surface.

Facile hydrothermal method to synthesise hexagonal rotor-like cerium carbonate hydroxide and CeO 2 nanostructures

The hexagonal rotor-like cerium carbonate hydroxide (CeCO3OH) and CeO2 nanostructures were successfully synthesised via a facile hydrothermal method using Ce(NO3)3 · 6H2O as the cerium resource, HNO3 additive to form an acidic solution, CO(NH2)2 as both precipitator and carbon source and polyvinylpyrrolidone as surfactant. Characterisation techniques using an X-ray diffractometer, scanning electron microscope, transmission electron microscope, X-ray photoelectron spectroscopy, thermogravimetric differential thermal analysis apparatus and UV–vis absorption spectrum have been used for studying the roles of Ce(NO3)3 · 6H2O and HNO3. It was found that the amount of Ce(NO3)3 · 6H2O has an obvious effect on the morphology of the as-synthesised CeCO3OH and CeO2 nanostructures, whereas HNO3 has a significant influence on the crystalline phase. CeO2 has a higher UV absorption than as-synthesised CeCO3OH, which is likely associated with the charge-transition between Ce3+ and Ce4+.

Study on Char Surface Active Sites and Their Relationship to Gasification Reactivity

Char gasification reactivity was considered to be proportional to the number of active sites in the char. Therefore, in this study, char surface active sites (including carbon active sites and catalytic active sites) were first measured with the help of the chemisorption process of CO2 at 300 °C, using a thermogravimetric apparatus. It was found that strong chemisorption (Cstr) and weak chemisorption (Cwea) of CO2, which relate to the presence of active inorganic components and organic matter of char, respectively, existed in this reaction procedure. A higher pyrolysis temperature and slower heating rate induced a decrease of both Cstr and Cwea. Then, char structure evolution was systematically investigated with multi-techniques, such as N2 adsorption isotherm, elemental composition, X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and energy-dispersive spectrometry (EDS) analysis, and attempts were made to correlate the measured structure parameters with CO2 chemisorption parameters. The results showed that a higher pyrolysis temperature and slower heating rate improved coal char C/H and C/O mole ratios, promoted the growth of the char crystalline structure and significant loss of functional groups, reduced the active mineral matters in the char, and consequently, resulted in a decrease of char surface active sites. Moreover, for both slow chars (SC) and rapid chars (RC), the activation energy decreased linearly with the increase of CO2 chemisorption parameters: Cstr, Cwea, and Cstr + Cwea. Hence, CO2 chemisorption parameters were better than the Brunauer–Emmett–Teller (BET) surface area to correlate with char reactivity.

Carbonation Behavior and the Reaction Kinetic of a New Dry Potassium-Based Sorbent for CO2 Capture

The carbonation behaviors of K2CO3 generated by calcination of KHCO3 were investigated with a pressurized thermo gravimetric apparatus, and the shrinking-core model in the noncatalytic heterogeneous reaction systems was used to explain the kinetics of the reaction between K2CO3, CO2, and H2O using analysis of the experimental breakthrough data. The carbonation reaction process can be divided into two stage-controlled regions, one is the surface chemical reaction-controlled region at the initial stage and another is the internal diffusion-controlled region at the last stage. The total amount of carbonation conversion is mainly dependent on the first stage. The reaction rate of this stage decreases as the reaction temperature increases. It increases in the same temperature when the CO2 and H2O concentrations increase. The total carbonation conversion decreases as the pressure increases. On the basis of the Arrhenius equation, the apparent activation energy and pre-exponential factor for these two stages are calculated, when the temperature is in the range of 55–80 °C and the pressure is 0.1 MPa. They are 33.4 kJ/mol and 3.56 cm/min for the surface chemical reaction-controlled region and 99.1 kJ/mol and 4.01 × 10–22 cm2/min for the internal diffusion-controlled region. This paper provides theoretical basis for the further study on the capture of CO2 from flue gas using dry potassium-based sorbents.

Reduction of Nickel Oxide Powder and Pellet by Hydrogen

Reduction of nickel oxide (NiO) powder and pellet by hydrogen was studied in a thermogravimetric apparatus. The variables studied were temperature (573, 673, 773, 873, 973 K) and hydrogen flow rate (100, 150, 200 cc min−1). With NiO powder 70–80 % reduction and with NiO pellets about 95 % reduction were achieved. With both NiO powder and pellets, the rate of reduction increased with increasing temperature and hydrogen flow rate and the linear nature of the fractional reduction versus time (F vs. t) plot, for the most part of the reduction at all temperatures, supported a rate control by gas film diffusion. The activation energies for the reduction of NiO powder and NiO pellet were found to be 20.14 and 19.21 kJ mol−1, respectively. The SEM images showed that the grain size of nickel (Ni) produced was 1–2 μ, and the XRD analysis established the presence of Ni (and the absence of NiO) in the reduced sample.

The Kinetic Analysis of Biomass Burning Based on Two-Component Reaction Model

Combustion of sawdust was studied using Pyris-1TGA thermogravimetric apparatus in the heating rates of 20, 40, 60K/min. The combustion process of sawdust includes three steps: losing water, precipitation and combustion of volatile, and carburization. A bicomponent parallel reaction model is created and used to simulate the combustion process of sawdust under the heating rate of 40K/min. Comparison of simulation and experimental results shows that the fitting curves are in good agreement with the experimental results

The Experimental Study on Combustion Characteristics of Corn Straw and Coal Gangue

With a thermo gravimetric analysis apparatus combustion characteristics experiments of coal residue cornstalk and mixtures of them were done at 20 C/min heating rate. Then the combustion characteristic Parameters were obtained by above experiments. The c combustion activation energies were acquired by kinetics analysis. The results show those: the ignition characteristic and synthesis combustion characteristic of coal residue are bad. The ignition characteristic and synthesis combustion characteristic of cornstalk are better. The combustion characteristics of the mixture of coal residue and cornstalk are determined by mixing ratio. The ratio of cornstalk is more and the synthesis combustion characteristic is better.

Study on the failure mechanism of potassium-based sorbent for CO 2 capture and the improving measure

With thermogravimetric apparatus (TGA), X-ray diffraction (XRD) and barium sulfate gravimetric methods, the carbonation reactivities of K 2CO 3 and K 2CO 3/Al 2O 3 in the simulated flue gases with SO 2 are investigated and the reaction equations are inferred. Results show that there are KHCO 3 and K 2SO 3 generated. The generation K 2SO 3 reduces the utilization ratio of the sorbent. H 2O may accelerates the sulfation reaction of AR K 2CO 3 as K 4H 2(CO 3) 3·1.5H 2O is generated in the reaction among K 2CO 3, SO 2 and H 2O. K 2SO 3 is directly generated from sulfation reaction of K 2CO 3/Al 2O 3, because there are K 2CO 3·1.5H 2O and K 2SO 3 generated in the reaction among K 2CO 3/Al 2O 3, SO 2 and H 2O. K 2CO 3·1.5H 2O does not react with SO 2, and K 2CO 3·1.5H 2O/Al 2O 3 reacts with SO 2 slowly. Compare with the reaction process without H 2O pretreatment, the reaction rates of KAl30 increased after H 2O pretreatment and the failure ratio is about a half of that without H 2O pretreatment. So, K 2CO 3/Al 2O 3 shows good carbonation and anti-sulfation characteristic after H 2O pretreatment.

Research on Combustion Characteristics of Cooking Oil Tar in Pipe by TG-FTIR Analysis

The pyrolysis characteristics of the cooking oil tar in an ambient air were investigated using a thermogravimetric apparatus with infrared-spectrum analyzer. Experimental results showed that the combustion process of cooking oil tar can be divided into five stages. The first step of mass loss is due to water evaporation. The second stage is the volatilization and combustion of the low boiling point compound，the third stage is the combustion of instauration hydrocarbon，the fourth stage is the combustion of ester and the last stage is the combustion of saturation hydrocarbon. A simple kinetic description, named in this work as ‘First Order Reaction and Three-dimensional Diffusion Separate-stage Model (O1+D3)’ model, was developed based on the experimental results and integral analysis method.

Curie temperature of nickel

Nickel presents a magnetic transition ferromagnetic/paramagnetic with a variation of temperature; this transition is classified as a second order transition using the Ehrenfest criteria. The end of this transition is characterized by a point called Curie point. This temperature is used for the calibration of thermogravimetric apparatus. As the Curie temperature is not a fixed point, no scientific authority has decided what the temperature of this point is. As different values are proposed in the literature, it appeared that it was necessary to further explore measurement of this point.

Study on High-Temperature Oxidation Characteristics of Pure Vanadium

The pure vanadium specimen of 99.65% relative density was prepared by hot isostatic pressing. The initial oxidation characteristics and constructions of pure vanadium at different temperatures were analyzed by thermogravimetric test apparatus (TGA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results show that the oxidation process and oxygen uptake of pure vanadium follow parabolic kinetics. The activation energy for the oxidation process is 118KJ/mol. With the rising of temperature, the predominant oxide phases are VO0.03, VO2 and V2O5 in turn. Under 500°C , the specimens’ surface morphology is densely distributed. While at 600°C , the fine fish-scale-shaped morphology is evenly distributed.

Analysis of the vaporization process in TG apparatus and its incidence in pyrolysis

An analysis of the evaporation process of n-hexadecane in a thermogravimetric apparatus was carried out. n-Hexadecane represents a typical example of a high boiling point compound and its study is interesting for understanding those processes where vaporization takes place in parallel with pyrolysis during thermal treatment. The process has been studied under different operating conditions: nitrogen and air atmospheres, and isothermal and dynamic runs with three different heating rates from 5 K/min to 20 K/min. The experimental data were satisfactorily correlated to a n-order model with zero process order and the same apparent activation energy for all runs, but the exponential factors of the different runs depended on the initial mass and the heating rate. The experimental results were compared with those predicted considering the diffusion process inside the crucible, taking into account the vapor pressure and the diffusion coefficient of n-hexadecane. A parameter, product of these two variables, can be estimated from a single TG run, so the vaporization process in other equipment and/or operating conditions can also be estimated.